1. Field of the Invention
The present general inventive concept relates to a developing unit and an image forming apparatus having the same, and more particularly, to a developing unit having an improved developer feeding configuration and an image forming apparatus having the same.
2. Description of the Related Art
In general, a color image forming apparatus scans light onto an image receptor having a predetermined electric potential to form an electrostatic latent image, spreads a color developer on the electrostatic latent image and transfers and fuses the same on a printing medium to form a color image. The color of the developer used for the color image forming apparatus generally includes yellow, magenta, cyan, and black.
The color image forming apparatus is classified into a single-path type and a multi-path type. The multi-path type image forming apparatus employs a single exposure part, a single electrifying unit and four developing units for developing each of the colors. A color image is formed by rotating the image receptor four times. Accordingly, the multi-path type image forming apparatus printing time is four times longer than the single-path type image forming apparatus. On the other hand, the multi-path type image forming apparatus has the advantage of having a simple configuration, and a lower manufacturing cost since it employs a single exposure part and a single electrifying unit.
FIG. 1 is a schematic view illustrating a structure of a conventional multi-path type color image forming apparatus 10. As illustrated in FIG. 1, the image forming apparatus 10 includes an image receptor 20 electrified by an electrifying unit (not shown), an exposure part (or light scanning unit) 40 which scans light onto the image receptor 20 to form an electrostatic latent image, and a developing device 30 which supplies developer to the electrostatic latent image of the image receptor 20 to form a visible image thereon.
Here, the developing device 30 includes plural developing units 30K, 30Y, 30M and 30C, corresponding to colors of the developer stored therein, here for example, the colors of cyan, magenta, yellow, and black. Also, each of the developing units includes a casing 31, a developer feeding unit 32 which is disposed to face the image receptor 20 and spreads developer on the electrostatic latent image, a supplying part 33 which supplies the developer to the developer feeding unit 32, and a developer feeding part 35 which feeds the developer accommodated inside the casing 31 to the supplying part 32.
As illustrated in FIG. 2, the conventional developer feeding part 35 includes a plurality of agitators 35a, 35b, 35c, and 35d disposed to be parallel with each other for feeding the developer. That is, the developer is sequentially fed from the agitator 35a furthest from the developer feeding unit 32 to the agitator 35d closest to the developer feeding unit 32. However, in the conventional developer feeding part 35 with this configuration, the plurality of agitators 35a, 35b, 35c, and 35d should be rotated in the same direction to feed the developer smoothly, and the rotating speed of the agitator 35 should be increased from agitator 35a to agitator 35d. 
Accordingly, there has been a problem that a power transmission part for transmitting a driving force has a complicated configuration, and in order to rotate the plurality of agitators at optimum speed, the driving part is apt to be overloaded.
In addition, these problems may become more aggravated when it is desired to minimize the size of the image forming apparatus by reducing the height of the developing unit casing, since the number of agitators for feeding the developer should be increased.
Furthermore, if the number of the agitators increases, the time during which the developer contacts with the agitators increases. When this contacting time with the agitators increases, the stress applied to the developer by frictional forces increases, thereby deforming the developer and thus the printing quality deteriorates.